diff --git a/bin/disinto b/bin/disinto
index c594adc..83454c2 100755
--- a/bin/disinto
+++ b/bin/disinto
@@ -155,7 +155,8 @@ generate_compose() {
 
   cat > "$compose_file" <<'COMPOSEEOF'
 # docker-compose.yml — generated by disinto init
-# Brings up Forgejo, Woodpecker, Dendrite (Matrix), and the agent runtime.
+# Brings up Forgejo, Woodpecker, and the agent runtime.
+# Dendrite (Matrix) is added only when init is called with --matrix.
 
 services:
   forgejo:
@@ -213,16 +214,6 @@ services:
     networks:
       - disinto-net
 
-  dendrite:
-    image: matrixdotorg/dendrite-monolith:latest
-    restart: unless-stopped
-    volumes:
-      - dendrite-data:/etc/dendrite
-    environment:
-      DENDRITE_DOMAIN: disinto.local
-    networks:
-      - disinto-net
-
   agents:
     build: ./docker/agents
     restart: unless-stopped
@@ -238,21 +229,18 @@ services:
     environment:
       FORGE_URL: http://forgejo:3000
       WOODPECKER_SERVER: http://woodpecker:8000
-      MATRIX_HOMESERVER: http://dendrite:8008
       DISINTO_CONTAINER: "1"
     env_file:
       - .env
     depends_on:
       - forgejo
       - woodpecker
-      - dendrite
     networks:
       - disinto-net
 
 volumes:
   forgejo-data:
   woodpecker-data:
-  dendrite-data:
   agent-data:
   project-repos:
 
@@ -284,6 +272,70 @@ COMPOSEEOF
   echo "Created: ${compose_file}"
 }
 
+# Append Dendrite (Matrix) service to docker-compose.yml and generate config.
+# Called only when --matrix flag is passed to init.
+append_dendrite_compose() {
+  local compose_file="${FACTORY_ROOT}/docker-compose.yml"
+  local dendrite_config_dir="${FACTORY_ROOT}/docker/dendrite"
+  local dendrite_yaml="${dendrite_config_dir}/dendrite.yaml"
+
+  mkdir -p "$dendrite_config_dir"
+
+  # Generate a minimal dendrite.yaml
+  cat > "$dendrite_yaml" <<'DENDRITECFG'
+# dendrite.yaml — generated by disinto init --matrix
+version: 2
+global:
+  server_name: disinto.local
+  private_key: matrix_key.pem
+  database:
+    connection_string: file:dendrite.db
+  cache:
+    max_size_estimated: 512mb
+  jetstream:
+    storage_path: /etc/dendrite/jetstream
+client_api:
+  registration_disabled: true
+DENDRITECFG
+  echo "Created: ${dendrite_yaml}"
+
+  # Append dendrite service before the volumes: section
+  python3 -c "
+import sys, pathlib
+p = pathlib.Path(sys.argv[1])
+text = p.read_text()
+dendrite_service = '''
+  dendrite:
+    image: matrixdotorg/dendrite-monolith:latest
+    restart: unless-stopped
+    volumes:
+      - dendrite-data:/etc/dendrite
+      - ./docker/dendrite/dendrite.yaml:/etc/dendrite/dendrite.yaml:ro
+    environment:
+      DENDRITE_DOMAIN: disinto.local
+    networks:
+      - disinto-net
+'''
+# Insert dendrite service before 'volumes:' line
+text = text.replace('\nvolumes:\n', dendrite_service + '\nvolumes:\n', 1)
+# Add dendrite-data volume
+text = text.replace('  agent-data:', '  dendrite-data:\n  agent-data:')
+# Add MATRIX_HOMESERVER env var to agents service
+text = text.replace(
+    '      DISINTO_CONTAINER: \"1\"',
+    '      MATRIX_HOMESERVER: http://dendrite:8008\n      DISINTO_CONTAINER: \"1\"'
+)
+# Add dendrite dependency to agents service
+text = text.replace(
+    '      - woodpecker\n    networks:',
+    '      - woodpecker\n      - dendrite\n    networks:'
+)
+p.write_text(text)
+" "$compose_file"
+
+  echo "Updated: ${compose_file} (added Dendrite service)"
+}
+
 # Generate docker/agents/ files if they don't already exist.
 generate_agent_docker() {
   local docker_dir="${FACTORY_ROOT}/docker/agents"
@@ -1162,7 +1214,7 @@ disinto_init() {
   shift
 
   # Parse flags
-  local branch="" repo_root="" ci_id="0" auto_yes=false forge_url_flag="" bare=false
+  local branch="" repo_root="" ci_id="0" auto_yes=false forge_url_flag="" bare=false enable_matrix=false
   while [ $# -gt 0 ]; do
     case "$1" in
       --branch)    branch="$2"; shift 2 ;;
@@ -1170,6 +1222,7 @@ disinto_init() {
       --ci-id)     ci_id="$2"; shift 2 ;;
       --forge-url) forge_url_flag="$2"; shift 2 ;;
       --bare)      bare=true; shift ;;
+      --matrix)    enable_matrix=true; shift ;;
       --yes)       auto_yes=true; shift ;;
       *) echo "Unknown option: $1" >&2; exit 1 ;;
     esac
@@ -1253,6 +1306,9 @@ p.write_text(text)
     forge_port=$(printf '%s' "$forge_url" | sed -E 's|.*:([0-9]+)/?$|\1|')
     forge_port="${forge_port:-3000}"
     generate_compose "$forge_port"
+    if [ "$enable_matrix" = true ]; then
+      append_dendrite_compose
+    fi
     generate_agent_docker
   fi
 
@@ -1344,10 +1400,13 @@ p.write_text(text)
     echo ""
     echo "── Starting full stack ────────────────────────────────"
     docker compose -f "${FACTORY_ROOT}/docker-compose.yml" up -d
-    echo "Stack:   running (forgejo + woodpecker + dendrite + agents)"
-
-    # Provision Matrix now that Dendrite is running
-    setup_matrix
+    if [ "$enable_matrix" = true ]; then
+      echo "Stack:   running (forgejo + woodpecker + dendrite + agents)"
+      # Provision Matrix now that Dendrite is running
+      setup_matrix
+    else
+      echo "Stack:   running (forgejo + woodpecker + agents)"
+    fi
 
     # Activate repo in Woodpecker now that stack is running
     activate_woodpecker_repo "$forge_repo"